Method of improving detergency of alkylphenol polysulfonates by base precipitation and separation

ABSTRACT

PROCESS FOR ENHANCING THE DETERGENCY OF LINEAR ALKYLPHENOL POLYSULFONATE DETERGENT ACTIVES CONTAINING FROM 25 TO 50 MOL PERCENT OF PARA-ALKYL MATERIALS WHICH COMPRISES MIXING SUFFICIENT BASE WITH THE MATERIAL IN AQUEOUS SOLUTION TO FORM A PRECIPITATE AND REMOVING THE PRECEIPITATE.

United States Patent METHOD OF HVIPROVING DETERGENCY 0F ALKYLPHENOLPOLYSULFONATES BY BASE PRECIPITATION AND SEPARATION Eric D. Hannah, MillValley, Califl, assignor to Chevron Research Company, San Francisco,Calif. No Drawing. Filed Mar. 16, 1971, Ser. No. 124,424 Int. Cl. Clld1/22 US. Cl. 260-512 R 6 Claims ABSTRACT OF THE DISCLOSURE Process forenhancing the detergency of linear alkylphenol polysulfonate detergentactives containing from to 50 mol percent of para-alkyl materials whichcomprises mixing suflicient base with the material in aqueous solutionto form a precipitate and removing the precipitate.

BACKGROUND OF THE INVENTION This invention is concerned with a processfor producing heavy duty detergents which perform effectively in theabsence of phosphate builders.

The concern over increasing growth of algae in the nations streams andlakes has caused a search to be made for detergents which will performwithout the use of additional phosphate building compounds such assodium polyphosphate. These materials are believed to be a cause of thealgae growth and consequent eutrophication.

In US. patent application Ser. No. 34,886, filed May 5, 1970, there aredisclosed and claimed polysulfonated alkylphenols which perform thedesired heavy duty phosphate-free washing quite effectively. Thesecompounds are of the formula:

in which R is linear alkyl of 16 to 22 carbon atoms, X is H or awater-soluble salt-forming cation, n is at least 1.5, and not more than25 mol percent of the sulfonated alkylphenols have R attached on thearomatic nucleus in a position para to OX.

These materials are produced by the sulfonation of appropriatealkylphenols followed by neutralization with a suitable salt-formingcation. Thus the salt-forming cation X may be alkali metal, alkalineearth metal, ammonium, or various organic cations. The alkylphenols usedmust have a low para-alkyl content (less than 25 mol percent) and thusare usually prepared by specific alkylation processes which produce highortho content compounds. Included among the ortho alkylation techniquesare thermal alkylation and the utilization of various catalysts such asaluminum, magnesium, hydrogen fluorine-treated aluminum silicate, alkylsulfonic acids, etc.

Phenol alkylation using conventional acidic catalysis such as theFriedel-Crafts catalysts, including aluminum chloride, zinc chloride,ferric chloride, etc., produces alkylphenols in which the para isomercontent is generally from to 50%. Upon sulfonation these materials donot form satisfactory detergents. It is therefore desirable to provide amethod for improving the products derived from the conventionallyproduced alkylphenol mixtures into useful, effective detergents.

SUMMARY OF THE INVENTION A process is provided for converting linearalkylphenol polysulfonate mixtures having a high proportion of paraalkyl content into mixtures having improved detergency,

ice

the mixtures produced being suitable for use as heavy duty detergentactives. This is accomplished by mixing base with an aqueous solution ofalkylphenol polysulfonates of the formula in which R is linear alkyl of16 to 22 carbon atoms, from about 25 to about 50 mol percent of which isattached in a position para to OX, X is H or a Water-soluble saltformingcation, and n is at least 1.5, the base being added in sufficientquantity to form a precipitate, and separating the precipitate whichforms. The separation of the precipitate may be accomplished byfiltration, centrifugation, or other conventional techniques forseparating solid and liquid phases.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The aqueous solution ofpolysulfonate should have a concentration of between about 1 and 50weight percent, preferably between about 5 and 25 weight percent.

Bases which can be added to raise the pH of the solution to the properrange include the oxides and hydroxides of alkali metals and alkalineearth metals as well as various organic base materials. The preferredmaterials are the alkali metal hydroxides and oxides. The preferredmaterial is sodium hydroxide. The bases may be added directly to thesolution or may themselves be in aqueous solution when added.

As previously noted, the precipitate which forms upon base addition canbe removed by any suitable technique, e.g. settling and decantation,filtration or centrifugation. However, it is preferred that theprecipitated material be removed by centrifugation, as, due to thegelatinous nature of some of the precipitates, filtration is ratherdifficult to perform.

The alkylphenols which are employed to produce the polysulfonates whichin turn are employed in the processes of this invention are thosederived by the alkylation of phenol with olefins, halides, or alcoholsusing conventional acid catalysis. The catalysts which are employed aretypically the Friedel-Crafts type catalysts including aluminum chloride,zinc chloride, ferric chloride, etc., and other acidic catalysts such asactivated clay and hydrogen fluoride. The alkylphenols produced byalkylation with these materials typically have para alkyl contents ofbetween about 35 and 50% The sulfonation of the alkylphenols to producethe feed compounds of this invention may be accomplished by any suitablemethod. Thus, sulfonating agents which may be reacted with thealkylphenol include chlorosulfonic acid, oleum, or sulfuric acid. It isonly important that enough sulfonating agent be employed to incorporatean average of at least 1.5, preferably 1.6 atoms of sulfur (in the formof sulfonate groups) into each molecule. That is, over one-half of themolecules are disulfonated. Each sulfonate group incorporated into thesealkylphenols can be measured as a surface active site by titration. Thisnumber is referred to as active group incorporation (AGI). Sulfonationwith oleum is preferred.

The sulfonation is usually accomplished with a ratio of at least 2 andpreferably from 4 to 10 mols of available S0 from the sulfonating agentto one mol of the alkylphenol. The use of a solvent is ordinarily notrequired in carrying out the sulfonation. The alkylphenol and thesulfonating agent are simply mixed and the reaction is allowed toproceed. maintaining the temperature of the reaction mixture within thedesired limits. The time required for disulfonation will be dependentupon the reaction temperature, the sulfonating agent, the ratio ofsulfonating agent to alkylphenol, and the total quantity of reactantspresent. The reaction is usually etfected at a temperature in the rangeof to 150 0., preferably 25 to 100 C.

The processes of the invention are described in the following examples:

EXAMPLE 1 Precipitation of alkylphenol polysulfonates by a base TABLE IAlkylphenol disulfonate Percent ofpH at .Alkyl chain initial lengtho-Alkyl p-Alkyl clouding ca. 65 ca. 35 9. 6

62 38 9. 5 ca. 65 ea. 35 9. 4 67 33 9. 6 95 5 It was noted that each ofthe materials in which the phenol contained over 25% of the p-alkylisomer formed a precipitate while the materials having less than thisamount of p-alkyl isomer did not form a precipitate even at a pH of13.5.

EXAMPLE 2 Isolation of a high detergency alkylphenol polysulfonate bybase addition The feed stock for this experiment was an aqueous solutioncontaining 6.7% by weight of alkylphenol polysulfonate in which thealkyl groups contained from 18 to 20 carbon atoms, and were attachedabout 62% ortho and 38% para. The sulfonates contained an average of 1.8sulfonate groups per molecule. Four 40-ml. portions were placed in fourcentrifuge tubes. To each tube was added 3 ml. of 2.5 N NaOH and allwere centrifuged. A heavy oily brown layer of about 1 ml. volume settledto the bottom in each tube. The supernatant liquid was separated andanalyzed. The concentration of the polysulfonate in the supernatantsolution was found to be about 3.6% based on original volume. Therefore,54% of the original active remained in solution and the separatedprecipitate contained 46% of the active. Detergency of the originalcomposition and of both the precipitate and filtrate materials weredetermined by the following procedure.

Detergency of the compounds produced by the process of the presentinvention is measured by their ability to remove natural sebum soil fromcotton cloth. By this method, small swatches of cloth, soiled by rubbingover face and neck, are washed with test solutions of detergents in aminiature laboratory washer. The quantity of soil removed by thiswashing procedure is determined by measuring the reflectances of the newcloth, the soiled cloth, and the washed cloth, the results beingexpressed as percent soil removal. Because of variations in degree andtype of soiling, in water and in cloth, and other unknown variables, theabsolute value of percent soil removal is not an accurate measure ofdetergent eifectiveness and cannot be used to compare variousdetergents. Therefore, the art has developed the method of usingrelative detergency ratings for comparing detergent effectiveness.

The relative detergency ratings are obtained by comparing andcorrelating the percent soil removal results from solutions containingthe detergents being tested with the results from two defined standardsolutions. The two standard solutions are selected to represent adetergent system exhibiting relatively high detersive characteristicsand a system exhibiting relatively low detersive characteristics. Thesystems are assigned detergency ratings of 6.3 and 2.2 respectively.

By washing portions of each soiled cloth with the standardizedsolutions, as well as with two test solutions, the results can beaccurately correlated. The two standard solutions are identical informulation but are employed at different hardnesses.

STANDARD SOLUTION FORMULATION The standard exhibiting high detersivecharacteristics (Control B) is prepared by dissolving the aboveformulation (1.0 g.) in one liter of 50 p.p.m. hard water (calculated ascalcium carbonate and /a magnesium carbonate). The low detersivestandard (Control A) contained the formulation (1.0 g.) dissolved in oneliter of p.p.m. water (same basis).

A miniature laboratory washer is so constructed that four diiferentsolutions can be used to wash different parts of the same swatch. Thisarrangement ensures that all four solutions are working on identicalsoil (natural facial soil). Relative detergency ratings (RDRs) arecalculated from soil removals (SRs) according to the equation:

RDR=22 +4.1

A further refinement in the determination of relative detergency ratingswas developed. In this method, instead of employing two standardformulations, one of the formulations used in preparing the four testsolutions had a known relative detergency rating (RDR) which had beendetermined by the above formula. Relative detergency ratings of theother three formulations were then determined by comparing the percentsoil removal (SR) of these formulations with that of the knownformulation.

Table II presents detergency data on a group of the products obtained inExample 2 including the original mixture, the precipitate, the filtrate,and for comparison the detergency rating is given for a linearalkylbenzene sulfonate (LAS) having from 11 to 14 carbon atom straightchain alkyl groups. The LAS data are given both with and withoutphosphate builder.

Each formulation tested comprised 25 weight percent of the test materialalong with 1% carboxymethylcellulose, 7% sodium silicate, 8% water, and59% sodium sulfate. The LAS comparison formulations were prepared in thesame way, except that in the phosphate-containing example only 20% ofLAS was used and most of the sodium sulfate was replaced by an equalamount of sodium triphosphate, thereby producing a formulation having40% triphosphate and 19% sulfate, both as sodium salts. The test resultswere obtained at a pH of 7 except for the two LAS examples, which wererun at a pH of 9 (without phosphate) and 10 (with phosphate).

LAS (20%) sodium triphosphate (40%).. 5.7 3.7 Example 2:

Original mixture 4. 7 0. 2

Preclpitate 2. 8 0.

ate 5. 2. 2

It may be noted that the relative detergency of the filtrate of ExampleII is significantly better than that of the original material. Thisimprovement is obtained by base precipitation and removal of theprecipitate (which displayed essentially no detergency in hard Water).

While the character of this invention has been described in detail withnumerous examples, this has been done by way of illustration only andwithout limitation of the invention. It will be apparent to thoseskilled in the art that modifications and variations of the illustrativeexamples may be made in the practice of the invention within the scopeof the following claims.

What is claimed is:

1. A method for improving the heavy duty detergency of an alkylphenolpolysulfonate of the formula in which R is linear alkyl of 16 to 22carbon atoms and from about 25% to being attached in a position para toOX, X is H or a alkali metal, alkaline earth metal or ammonium cation, nis an average of at least 1.5, said method comprising the steps ofmixing sufficient base With an aqueous solution containing from 1 to 50weight percent of said polysulfonate to form a precipitate in thesolution, and separating the precipitate from the solution andrecovering th'e supernatant liquid.

2. The method of claim 1 in which the base employed in an alkali metaloxide or hydroxide.

3. The method of claim 2 in which the base is sodium hydroxide.

4. The method of claim 1 in which the polysulfonate is present in theaqueous solution in an amount of from about 1 to 25 weight percent.

5. The method of claim 4 in which the polysulfonate is present in theaqueous solution in an amount of from about 5 to 15 weight percent.

6. The method of claim 1 in which the precipitate is separated from theaqueous solution by centrifugation.

References Cited UNITED STATES PATENTS 2,249,757 7/ 1941 Flett 2605122,205,946 6/1940 Flett 260--512 2,205,948 6/1940 Flett 260512 2,233,4083/1941 Flett 260505 2,283,199 5/ 1942 Flett 260505 LEON D. ROSDOL,Primary Examiner P. E. WILLIS, Assistant Examiner US. Cl. X.R. 25 25 5 8

